Prevalence and trends of vitamin D deficiency among patients undergoing testing at the Maternity and Children Hospital, Dammam, Eastern Province of Saudi Arabia (2023-2025).

Background: Vitamin D deficiency (VDD) remains widespread throughout the Middle East despite abundant sunlight. Saudi Arabia reports some of the highest burdens across age groups, with national surveys and cohort studies documenting very high combined rates of deficiency and insufficiency. Lifestyle factors, including limited sun exposure, indoor living, and low physical activity, are consistently implicated. Although high prevalence has been reported among adolescents and women of reproductive age, vitamin D deficiency affects multiple population groups. Earlier evidence from the Eastern Province reported very low circulating 25-hydroxyvitamin D levels despite its coastal latitude, suggesting that behavioral and cultural factors may outweigh geographic advantages. Recent local data continue to show a substantial burden of suboptimal vitamin D status in clinical populations, with nearly half of tested individuals deficient and only about one-fifth achieving sufficient levels, although modest improvements in vitamin D status have been observed over recent years. Methods: We conducted a retrospective cross-sectional analysis of all serum 25-hydroxyvitamin D [25(OH)D] results measured by CMIA ARCHITECT (Chemiluminescent Microparticle Immunoassay) extracted from the laboratory information system at the Maternity and Children Hospital in Dammam from 1 January 2023 to 31 August 2025. The study population reflects routine clinical testing and includes a heterogeneous mix of pediatric, adolescent, and adult patients. For each calendar year, one index observation per patient was retained. Concentrations were reported in nanomoles per liter (nmol/L). Vitamin D status categories were prespecified as follows: severe deficiency <17.5 nmol/L, deficiency <50 nmol/L, insufficiency 50-74 nmol/L, and sufficiency ≥75 nmol/L. Prevalence was calculated overall and stratified by age group, sex, and year. Associations between vitamin D status and demographic variables were assessed using chi-square tests, and temporal trends were evaluated across study years. Multivariable logistic regression analysis was performed to examine independent predictors of vitamin D deficiency, including age group, sex, and year. Ethics approval was obtained with a waiver of informed consent due to the retrospective nature of the study. Results: The analytic cohort comprised 14,369 index measurements and reflects a mixed clinical population undergoing routine vitamin D testing. The mean serum 25(OH)D concentration was 56.5 ± 32.6 nmol/L. Overall, 49.1% of results were classified as deficient (<50 nmol/L), 27.4% as insufficient (50-74 nmol/L), 21.2% as sufficient (≥75 nmol/L), and 2.2% as severely deficient (<17.5 nmol/L). Vitamin D deficiency remained highly prevalent across the cohort. Females demonstrated slightly higher rates of deficiency compared with males (50.7% vs. 48.1%, Conclusion: Vitamin D deficiency and insufficiency remain highly prevalent among patients tested in this mixed hospital-based population in the Eastern Province. Nearly half of individuals were deficient and over one quarter were insufficient, while only about one fifth achieved sufficient vitamin D levels. Females showed slightly higher rates of deficiency, and modest improvements in vitamin D status were observed across study years. These findings support the need for continued public health measures including routine counseling on safe sun exposure, appropriate vitamin D supplementation across at-risk groups, and sustained food-fortification and awareness programs. Future research should incorporate additional determinants such as anthropometry, dietary intake, supplement use, sun exposure, and genetic factors to better inform targeted interventions.